SOURCE

//while循环
var i = 1;
var wd = 0;
while(i<=100){
wd = wd + i;
i++;
}
document.write(wd);
document.write("<br />");



//for循环
var i = 1;
var wd = 0;
for(;i<=100;i++){
wd = wd + i;
}
document.write(wd);
document.write("<br />");



//do while 循环
var wd = 0;
var i = 0;
    do {
            i++;
            wd += i;
        }
        while (i <= 100);

document.write(wd);